Transformer construction



Aug. 13 9 0- R. s. EDWARDS 2,211,691

TRANSFORMER CONSTRUCTION Filed Sept. 17, 1938 2 Sheets-Sheet l INVENTOR1 055427 8. foam/e05 1 5 BY 1 A 33 MI W ATTO NEY R. 5. EDWARDSTRANSFORMER CONSTRUCTION Filed Sept. 17, 1938 Aug. 13, 1940.

2 Sheets-Sheet 2 llm mum INVENTOR P0552? S 'qa/Ae s Patented Aug. 13,1940 UNITED STATES TRANSFORMER CONSTRUCTION Robert S. Edwards, NewCanaan, Conn, assignor to Edwards and Company, Inc., Norwalk, Conn, acorporation of New York Application September 17, 1938, Serial No.230,377

14 Claims.

This invention is concerned with transformer construction andinstallation, particularly of the low voltage type of transformer, suchas is employed in obtaining lower voltages from the usual type ofhousehold lighting or power circuit which is usually of 110 volts.

One of the objects of this invention is to provide a transformer andinstallation construction whereby cost of manufacture and cost to theconsumer may be reduced, manufacturing processes simplified, quickerassembly in manufacture achieved, and less cost and greater flexibilityand adaptability of installation achieved. Another object is to providea transformer construction capable of manufacture with a minimum oftools and hence tool cost, and yet capable of meeting varyingrequirements. Another object is to provide a transformer constructionand mounting or installation therefor capable of wide adaptability ofapplication to meet varying conditions or requirements met with inpractical use.

Another object is to provide a transformer construction that will besimple, practical and dependable and yet well suited for the widelydiffering installation requirements met with, and thereby to avoid theexpense, inconvenience, and

other difllculties attendant upon having to provide a special orparticular transformer structure for each type or kind of mounting orinstallation. Another object is in general to improve upon transformerconstruction and mountings therefor and installations thereof. Otherobjects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction,combinations of elements, and arrangements of parts as will beexemplified in the structure to be hereinafter described and the scopeof the application of which will be indicated in the following claims.

In the accompanying drawings in which is shown a preferred embodiment ofthe transformer construction and several embodiments of mountings andinstallations, all by way of illustration:

Figure 1 is a perspective view partly broken away of a transformercasing section;

Figure 2 is a perspective view of a companion casing section;

Figure 3 is a perspective view of the transformer per se, namely thecore and windings;

Figure 4 is a perspective view of an assembly and mounting device;

Figure 5 is a transverse sectional view of the transformer wheninstalled according to one condition met with in practice;

Figure 6 is a sectional view through a wall box showing in end elevationanother type of trans former mounting and installation according to 6 myinvention;

Figure 7 is a perspective view of a barrier and mounting plate employedin Figure 6;

Figure 8 is a perspective view, on a smaller scale, of a different typeof outlet or wall box adapted according to other features of myinvention for a transformer mounting, and

Figure 9 is an elevation partly in section through the mounting plateas, for example, along the line 8-8 of Figure 6 or 99 of Figure 8,showing the interrelation between the transformer structure and theplate.

. Similar reference characters refer to similar parts throughout theseveral views in the drawmgs.

In Figure 3 I have shown a transformer T comprising a core l0 preferablylaminated and illustratively of the shell type, being provided,therefore, with appropriate core windows and a central core leg I Ithrough which and about which respectively the high and low voltagewindings, generally indicated at l2, extend. Illustratively, thetransformer may be for the purpose of reducing the volts of a householdlighting circuit to a lower voltage, such as 15 volts, for operatingrelays, bells, buzzers, etc.

The laminations of the core l0 comprise individual appropriately shapedstampings appropriately laid together to build up the core about thewindings I 2; the number of laminations and hence the thickness of coreemployed may vary according to the desired characteristics or capacityof the transformer, and according to certain features of my inventionthe casing structure later described is adapted to meet this variablecircumstance.

The casing preferably comprises two principal sections, generallyindicated at A and B in Figures 1 and 2, respectively. They arepreferably of identical shape, each accommodated to cover half of thetransformer T so that they may be initially stamped by the use of thesame dies, thus avoiding multiple sets of different tools.

Thus, section A is formed to provide a marginal portion l3 of sufiicientexpanse to rest against the face Ill (Figure 3) of the core III with itsperimeter matching that of the face l0, and with the portion l3 restingflat against the outer portions of facelll. Four flanges l4, l5, l6 andH, at right angles to the plane of the part I3 and each extending fromone of the four edges of the latter, relatively snugly overlapand'encase preferably not more than half of the sides of the core I0,acting also to hold the laminations of that fraction of the core l0against shifting.

The inner portions of the portion |3 are drawn in a direction away fromthe flanges |4, |5, l6 and I1 to form the bulging portion l8 to takeover the laterally projecting part of the windings l2 (see Figures 3 and5). This bulging portion I8 may be given any suitable shape,illustratively and preferably the shape, of a frustum of a pyramid, andon one of the inclined sides there- 01', such as the side l9 in Figure1, is mounted in any suitable manner, as by ears 2!) stamped out of thewall l9 itself, a suitable block or plate 2| of insulating materialappropriately apertured as indicated for insulatingly guiding throughsuitable apertures in the wall IS the insulated conductors C that leadfrom the high voltageecoil of the windings l2. This inclined wall l9permits the terminal conductors C and the insulating guiding means 2| tobe provided without consequential obstruction of the marginal casingportion 13 adjacent to it.

In two opposed parts of the marginal casing portion I3, as in the partsl3 and I3 I provide narrow elongated slots 22 and 23; these may be andpreferably are pierced in an operation separate from the stamping andforming steps in making up the sheet metal casing section A.

Casing section B is, as above'noted, identical to section A, having,therefore, a flat marginal portion l|3 to rest against the peripheralportions of the face Ill of the core- ID, with flang like parts H4, H5,H6 and M1 to take over the alined edges of the remaining half of thelaminations of core l0, and thus, like the flanges I4, l5, etc., ofsection A, may, be individually bent and joined together at their edgesor may be drawn to be continuous throughout; it has also arbulgingportion H8, again preferably in the shape of a frustum of a pyramid, andin one of its inclined faces, such as face H9, it has secured thereto asby ears I20, an insulating plate or block |2| carrying connectingterminals 24 in the form of binding screws, the terminals havingappropriate connection with the conductors E (Figure 5) which leadto thelow voltage coil of the windings l2.

At two opposed portions of the marginal portion H3, as in the portions||3 and H3 (Figure 2) I also provide slots and while they may beidentical to the slots 22 and 23 of Figure 1, so that the piercingoperation is the same, I prefer to provide in each portion two spacedslots 25, 26 and 21, 28.

When the two casing sections A and B are thus assembled to thetransformer T, it being noted that the horizontal spacing between theflanges l1 and i5 and H1 and H5 is slightly greater than the horizontaldimension of the core l0, slot 22 is brought into juxtaposition to thespaced slots 25-26 and slot 23 becomes sim ilarly related to spacedslots 21-28, being thus made ready for the reception of two preferablyidentical securing and mounting devices, one of which is shown in Figure4 where it is generally designated by the reference character F.

The device F is preferably made of sheet metal spaced to takerespectively into the slots 25 and 26 or 28 and 21.

The portion 30, at its end remote from the tongues 3|, 32, is providedwith suitable stop means to take against the marginal portion l3 of thecasing section A, and that stop means may comprise spaced flanges 33, 34which are preferably continued as at 33 and 34 along the extension 30"of the portion 30, extension 3!! being preferably tapered off ornarrowed down as indicated, terminating finally in a transverselyextending flange or foot 35 apertured as at 36, for a purpose laterdescribed. However, the extension 30 including the extensions 33 and 34of the flanges, is preferably scored along the line S so thatultimately, when desired, this extended portion may be broken off as bythe use of a pair of pliers.

The plate-like portion 30 has cut and bent out of it a relatively largetongue L, bent as shown to provide a crest or high point and ofsufficient length and width, in relation to the metal of the part F, togive it a resiliency or springiness of action for a purpose laterdescribed.

Utilizing two such members F, one of them is passed through slot 22 incasing section and in between the face |0 (Figure 3) of the core I andthe alined flange portions l1 and I I1 (see Figure 5), flanges 33 and 34thereby being brought into engagement with the marginal casing portionl3, the ears 3|, 32 of member F having passed through the slots 25 and26, respectively, in the marginal portion N3 of easing section B. In asimilar manner (see Figure 5) the other of the two members F is passedthrough the slot 23 of section A, passing between the face W of the corel0 and the alined flange portions l5 and 5 of the two casing sections,lugs or ears 3|, 32 passing through slots 28 and 21, respectively.

With the two marginal casing portions l3 and- I I3 resting respectivelyagainst the marginal portions of the core faces l0 and III, the twocasing parts are now suitably pressed toward each other, thuscompressing the laminated core I0, and depending upon the number oflaminations and hence thickness of the core, the juxtaposed edges of thetwo core-encasing flange casing parts l4, l5, etc., and H4, H5, etc.,are brought more or less toward each other; thereupon, so much of theears or lugs 3| and 32, there being four of them, as are left projectingbeyond the marginal casing portion 3 are bent over, as shown in Figure5, and against the adjacent side flanges which happen to be the parts 5and N1 of easing section B. Thereby, the three parts, namely, the twosimilar casing sections and the transformer T, become securely anddependably assembled and with the laminations of the core snugly andtightly clamped against shifting or displacement.

As the two securing devices F are assembled as above described, thespring tongues L thereof, being bent as shown and above described, by--pass the side flanges and remain spaced away from the alined sideflanges |1--l l1 and |5-| l5, respectively, as is better shown in Figure5.

If the transformer has to be mounted directly against or upon a flatsupporting surface, as indicated at 31 in Figure 5, the flange or feetportions 35, falling in the same plane and spaced sufliciently away fromthe plane of the bulge l8, may be rested against the supporting surfaceand the transformer construction secured to the latter as by screws 38passed through the apertures 36 in the feet. The low voltage terminals24 are where the transformer construction has to be mounted in an outletbox, such as the box 40 of Figure 6, seated in a recess 4| in ,a wall 42and provided "with suitable'lugs or angle plates 43 whereby, by theuseof screws 44 or the like, the box 40 may beheld in the recess 4| Wherethe box 40 is of usual or standard construction, it has lugs or ears,such as the ears. 45, provided with threaded holes-"spaced apart byastandard distance; in such'case, -I provide a plate 46 ofsuitably heavysheet metalhaving at its upper end (see Figure 6) suitable flange-likemeans, such as a single flange '41, wh0se ends are apertured as iii) at.48 and areadapted to rest respectively upon the-supporting lugs orflanges of the outlet box 40 to bring the holes 48 in registry with thethreaded holes in the lugs 45 for ultimate reception of the securingscrews 49.

Preferably the plate 46 is dimensioned to flt and preferably I stamp ahole H (Figures '7 and 6) in the plate, giving it the length and breadthof the central casingportion that is made up of the alined flanges l4,15, etc., and H4, H5, etc., of the casing sections A and B, but in twoopposed edges thereof I provide recesses 50 and 5!, spaced anddimensioned to permit the turned over portions of the lugs 3|, 32adjacent the low voltage face of the transformer freely to passtherethrough. Also, in each of these opposed edges of the hole H Iprovide a recess 52 of a length slightly greater than the width of thespring tongues L but the two recesses beingrespectively of such depthsthat the spacing between their bottom edges, as viewed in Figures 6 and7, is less than the maximum spacingbetween the high points or crests ofthe two members L of the transformer structure as the latter is seen inFigure 5 or in Figure 9.

Accordingly, the transformer construction of Figure 5, preferably. withthe leg extensions broken oil along the score lines S (see Figure 4) maybe passed into the hole H in the plate 46, and in the case of theparticular assemblage above described, with that end or casing sectionbearing the low voltage terminals 24 entering the hole H'first; theoverturned lugs 3!, 32 pass through by way of the recesses 50, 5| whencethe leading inclined portions of the two spring tongues L (see Figure.5) enter the opposed recesses 52, and yieldingly resist continuedpassage of the transformer structure further into the hole H. However,as pressure is continued to be exerted, the tongues L, L,due to theirspringiness, yield'or are cammed inwardly toward the transformer casingwalls, and thus the crests or high points of the tongues L are made topass through the hole H and to the other side of the plate 46,

- their springiness yieldingly urging them outwardly again. However,passage of the transformer assemblage through the hole H is precludedsince the flanges 33, 54 (Figure 4 and 9) project outwardly and act asstops to limit the extent to which the transformer construction canenter the hole H.

As is better seen from Figures 6-9, the end edges of these stop flangesterminate substantially in the plane of the marginal casing portion l4,thus bringing the plane of one face of the plate (see now Figure 9) intosubstantial alinement or coincidence with the plane of thecasing walll3.

L urges them in a direction away'from each other, bringing an inclinedportion of each into action against the bottom of the recess 52, thustending constantly to cam and urge the plate and the stop flanges 33, 34into contact and engagement with each other, and thus the assemblage isdependably maintained. a

The spring action of the parts L, L and their respective shapes may beso chosen that the as semblage of the transformer and the plate takesplace with a sort of snap action. The ultimate holding action is asecure one, though disassemblage may be effected upon applyingsuflicient pressure to cause the tongues-L to yield to permit thetransformer to be withdrawn from the hole H.

The mounting and barrier plate 45,with the transformer assembledthereto, may now be inserted into the box 40 and screws 49 employed tohold it in place. The low voltage terminal: 24 thereby become exposed inthe space to one side of the plate 45 and the high voltage conductors orconnectors C become exposed in the space cuit connections may be made inthe usual way, the walls of the box 40 being provided with ap- Thespring action of the latch-like tongues propriate knock-outs for'theentry and exit of the circuit conductors or' conduits. The flange 41(Figures 6 and '7) preferably also has spaced threaded holes 55 spacedappropriately, usually by a standard distance, to receive screws 56(Figure 6) by which a cover or finishing plate 5'! may be secured inposition, constructed preferably so as to overlap the wall surfacingabout the recess 4| in the wall.

Depending upon the character of the wiring system or other factors,other kinds or types of outlet or conduit boxes may be employed and towhich the transformer has to be related; in Figure 8 one such other typeof box is indicated at 58 by way of illustration and though shown to begenerally round it may be in any other shape. For relating thetransformer to such a box I employ a cover plate 59 apertured or slottedto receive the usual screws Bl] for securing the plate 59 in box-closingposition, but the plate 59 is provided with a hole H shaped, dimensionedand recessed like the hole H above described in connection with Figures7 and 9 and to the hole H the transformer may now be related in the sameway as described above with reference to Figures 7 and 9. Then theresultant assemblage of transformer and plate 59, with the high voltageside and hence the high voltage conductors C facing inwardly toward thebox and with the electrical connections thereto made, is related to thebox 58, and the screws 60 are put in place to complete the mounting,leaving the low voltage side and terminals 24 exposed outwardly of thebox whereby the low voltage circuit may be connected thereto. Hereagain, the leg portions or extensions of the member F of Figure 4 arepreferably V on the other side of the plate 45; respective cir- I videdin this invention a transformer construction and mounting orinstallation therefor in which the various objects heretofore noted, to-

gether with many thoroughly practical advantages, are successfullyachieved. It will be seen that I am enabled to have one transformerstructure, itself of simple and inexpensive manufacture, serve in asimple and practical way to meet, due to simple and inexpensive coactingstructural features, the widely varying requirements and peculiaritiesmet with in practice. Manufacturing processes are greatly simplified andinventories to be carried by jobbers and electricians may be muchsmaller than has heretofore, according to past practices been possible.

It will also be seen that a minimum of different tools need be providedfor manufacture of the devices, and by way of further example it will beseen that the hole H of Figures 6 and 7 may be punched in differentplates by the same tool or tools.

. Referring back to Figures 1-5, the spacing between the alined sideflanges l4-l I4 and iii-i I6 is preferably such as to snugly receivetherebetween the vertical dimension of the core I0 as the latter isviewed in Figure 3, while the spacing between the remaining opposedalined sides, namely l'I-Jll and I5-II5, is preferably as is bettershown in Figure 5, such that the horizontal dimension of the core I II,as viewed in Figure 3, plus the thicknesses of the two members F, issnugly receivable therebetween. When the lugs or ears 3l-32 are bentover, as shown in Figure 5, to hold'the laminations of the core clampedtogether with suflicient pressure, a strong and rigid transformer unitresults for the two mem-- bers F dependably hold the two casing sectionsA and B against transverse displacement of one with respect to theother. The members F are likewise rigidly and solidly secured, thuspermitting. dependable functioning of the parts F as supporting legswhen the installation is as in Figure 5. Should the requirement be for atransformer of greater capacity so as to require a core ill of greaterthickness, the same casing sections A and B maybe employed, the parts3|, 32 being of suiiicient length to function with such greaterthickness of core, and in such case there may be a greater spacingbetween the contiguous edge portions of the two casing sections.

In my co-pending application Serial No. 160,-

031, filed August 20, 1937, I have disclosed a transformer constructionhaving certain subject matter in common with the transformerconstruction disclosed in my presentv application; it is in my saidco-pending application that I make claim to such common subject matter.

As many possible embodiments may be made of the above invention and asmany changes might be made in the embodiment above set forth, it is to.be understood that all matter hereinbefore set forth, or shown in theaccompanying drawings, is to be interpreted as illustrative and not inlimiting sense.

I claim: a

1; In transformer construction, in combination, a transformer structurecomprising a core and windings that project from two opposed side facesof said core and two casing sections having portions to rest against themarginal portions respectively of said side faces and respectivelycovering over the projections of said windings, means comprising atleast two members that extend along opposed edge faces of said core andeach having direct connection with each of said casing sections to holdthem assembled to said core and to clamp'said sections and said coretogether, each of said two members having spring tongue means yieldablyprojecting therefrom each spaced from one of said edge faces and each ofsaid members having stop means projecting in a direction outwardly fromthe adjacent edge face, a transformer-supporting plate having anaperture shaped to permit said transformer structure to be passed intoit to an extent permitted by said 10 stop means, said spring tonguemeans yieldingas said structure is passed through the aperture to bringsaid stop means and plate in engagement v and acting to resist removalof the transformer structure from said aperture.

2. In transformer construction, in combination, a transformer structurecomprising a core and windings that project from two opposed side facesof said core and two casing sections having portions to rest against themarginal portions respectively of said side faces and respectivelycovering over the projections of said windings, means comprising atleast two members that extend along opposed edge faces of said core andeach having direct connection with each of said casing sections to holdthem assembled to said core and to clamp said sections and saidcoretogether, each of said two members having spring tongue meansyieldably projecting therefrom each spaced from one of said edge facesand each of said members having stop means projecting in a directionoutwardly from the adjacent edge face, whereby said transformerstructure may be mounted in an aperture of a plate with the latterengaging said stop means and said tongue means holding the structureagainst such relative displacements as might bring said stop means andplate out of engagement, said two members having extensions providedwith means whereby they may be secured to a wall surface or the like,said extension means being positioned and shaped so as not to interferewith the assembly of said transformer structure to said supportingplate.

3. A construction as claimed in claim 2 in which said two members aremade of sheet metal and said stop means of each comprises flange meansformed ,out of the sheet metal of each member.

4. In transformer construction, in combination, a transformer structurecomprising a core and windings that project from two opposed side facesof said core and two casing sections having peripheral portions to restagainst the marginal portions respectively of said side faces andrespectively covering over the projections of said windings, twosecuring members each comprising a flat sheet metal portion having stopmeans at one end thereof, said two securing members overlying twoopposed edge faces of said core, means comprising bent-over lug and slotmeans for securing said two securing members to opposed peripheralportions of said two casing sections, each of said securing membersbeing provided with spring means exposed externally of the casing andcore assemblage and presenting a crest spaced from said stop means.

5. In transformer construction, in combination, a transformer structurecomprising a core and windings that project from two opposed side facesof said ,core and two casing sections having peripheral portions to restagainst the marginal portions respectively of said side faces andrespectively covering over the projections of said windings, twosecuring members each comprising a flat sheet metal portionhaving stopmeans at 7 one end thereof, said two securing members overlying twoopposed edge faces of said core, means comprising bent-over lug and slotmeans for securing said two securing members to opposed peripheralportions of said two casing sections, at least one of said securingmembers having cut and bent out of said flat sheet metal portion atongue having a projecting portion spaced from said stop means by adistance substantially equal to or less than the thickness of asupporting member for said transform er construction, whereby saidsupporting member may be yieldably gripped between said projectingportion of said tongue and said stop means.

6. In transformer construction, in combination, a transformer structurecomprising a core and windings that project from two opposed side facesof said core and two casing sections having portions to rest against themarginal portions respectively of said side faces and respectivelycovering over the projections of said windings, said casing sectionsoverhanging said core at two opposed edge faces of the latter and in theoverhanging parts thereof being provided with registering slots, twosecuring members each comprisings a flat sheet .metal portion havingstop means at one end thereof and lug extensions at theother endthereof, each member being passed through the slot in the overhang ofone casing portion to the extent permitted by said stop means and havingthe lug extensions projected through the slots in the overhang of theother casing section to an extent accordingto the thickness ofthe core,said lug extensions being bent over to clamp saidcasing sections andcore 0 bent out of the plane thereof tongue meanstogether, at least oneof said casing sections having a flange-like extension overlapping theedge faces of said core and also said two securing members,said-securing members having cut and spaced from said stop means andoverlying said flange-like casing extension.

7. A sub-assembly for installation in a wall box that has at its opposedupper ends flange-like means having threaded holes, said sub-assemblycomprising a barrier plate of an expanse sufficient to fit thecross-sectional interiorof said box and having mounting means adapted torest against said opposed flange-like means and to be secured thereto byscrews threaded into said threaded holes, a transformer constructioncomprising a sheet metal casing receivable into said box but of smallercross-section than the interior of the latter, said barrier plate havingan aperture therein shaped substantially like that of a cross-section ofsaid transformer construction whereby the latter is receivable into saidaperture, said transformer construction having a plurality of sets ofspaced holding means be- 0 tween which edge portions of said aperturedbarrier plate are received and of which one holding means of each set ispositioned on one side of said cross-section to substantially limit theextent of entry of said transformer construction into said aperture andof which the other holding means of eachlset is positioned on the otherside of said cross-section, at least one of them being resilientlyyieldable and capable of yielding as said transformer construction isentered into said 7 aperture, thereby to hold said transformer con- 75comprising a barrier plate of an expanse sumcie'nt to fit thecross-sectional interior of said box and having mounting means adaptedto rest against said opposed flange-like means and to be secured theretoby screws threaded into said threaded holes, a transformer constructioncomprising a sheet metal casing receivable into said box but of smallercross-section than the interior of the latter, said barrier plate havingan aperture therein shaped substantially like that of a cross-section ofsaid transformer construction whereby the latter is receivable into saidaperture, said transformer construction having stop means positioned onone side of said cross-section to limit the extent of entry of saidtransformer construction into said aperture and having spring meanspositioned on the other side of said crosssection and capable ofyielding as said transformer construction and said spring means arepassed into said aperture to bring said stop means into engagement withsaid plate and thereafter holding said transformer construction againstmovement out of said aperture.

9. In transformer construction, in combination, a transformer structurecomprising a core and windings that project from two opposed side facesof said core and sheet metal casing means enveloping said core andwindings and having portions to rest against the marginal portionsrespectively of said side faces with bulges therein respectivelycovering the projections of said windings, and sheet metal meansseparate from said casing means and for mounting said structure onto asupporting surface, said last-mentioned means comprising two parallelsheet metal portions separate from said sheet metal casing means andextending respectively along and parallel to two opposed edge faces ofsaid structure and each being of a width commensurate with the length ofits adjacent edge face and of a length to extend beyond one of saidbulges in said casing means to form supporting legs for engagement withsaid supporting surface and being provided with means for securing it tothe supporting surface, said portions having flange means extending atan angle to the plane of the sheet metal thereof, said flange meansreinforcing said portions against bending about an axis intersecting theflange means and lying in the plane of the sheet metal of the respectiveportions, and said flange means of said two parallel portions restingrespectively against those portions of said casing means that restagainst the marginal portion of one of said side faces of said core, andbent-over lug means to hold said parallel portions against movement in adirection to disengage said flange means from said casing means.

10. A construction as claimed in claim 2 in which said extensions ofsaid two members are respectively joined to the latter by weakenedportions whereby said extensions may be broken off when said transformerstructure is mounted in the aperture of a plate as aforesaid.

11. In transformer construction, in combination, a transformer structurecomprising a core and windings and a casing therefor that comprises atleast two casing sections for respectively taking over substantiallyhalf portions of said core and windings, a plate for interrelation withsaid transformer structure, said plate having an aperture into whichsaid structure is receivable, and means for securing said casingsections and core together, said securing means comprising two sheetmetal members extending respectively along and substantially parallel totwo opposed edge faces of the core, means connecting each mentionedspaced parts being resilient so that '11; yields as said transformerstructure is entered 'into said aperture in order thereby to by-pass theedge portion of the plate.

12. In transformer construction, in combination, a transformer structurecomprising a core and windings and a sheet metal casing therefor,

,said sheet metal casing having, at two opposed sides thereof,extensions forming spaced leg-like standards by which the structure maybe secured to a supporting surface or the like, said two leg-likestandards having weakened portions whereby they may be severed or brokenofl, each of said two extensions having, on the casing sides of saidweakened portions, two spaced parts spaced apart by a distancesubstantially on the order of the thickness of an apertured mountingplate into whose aperture the transformer structure is insertable forsupport so as to receive opposed edges of the aperture between thespaced parts of said sides.

13. A transformer construction as claimed in claim 12 in which saidextensions have each flanges to give them rigidity and to form at leastone of the spaced parts of each of said opposed sides.

14. A transformer construction as claimed in claim 12 in which saidextensions have each flanges to give them rigidity and to form at leastone of the spaced parts of each of said opposed

